In the related art, CO2 recovery units that recover CO2 exhausted from boilers or the like of thermoelectric power plants are suggested (for example, refer to PTL 1). In the CO2 recovery units, flue gas is introduced into a CO2-absorber, a CO2-absorbing solution is brought into contact with CO2 included in the flue gas so that CO2 is made to be absorbed thereinto. The CO2-absorbing solution that has absorbed CO2 is sent to a CO2-regenerator and is decarboxylated with heating by a regeneration heater that regenerates the CO2-absorbing solution, and thereby, a high-concentration CO2 gas is recovered. The CO2-absorbing solution after the decarboxylation is supplied to the CO2-absorber by a liquid feed pump, and the CO2-absorbing solution is circulated and used between the CO2-absorber and the CO2-regenerator.